Mercury feed-through cord switch



Nov. 8, 1960 2,959,656

A. R. BENTSEN MERCURY FEE-THROUGH CORD SWITCH Filed March 4, 1958 fy Wffii A43 A/fmm/ United States Patent MERCURY FEED-THROUGH CORD SWITCH Arthur R. lfentsen, Liverpool, N.Y., assignor to General Electric Company, a corporation of New York Filed Mar. 4, 1958, Ser. No. 719,110

6 Claims. (Cl. 200-152 The present invention relates to mercury switches and particularly to a mercury feed-through cord switch for controlling the operation of table lamps in the home. Feed-throughcord switches of the mechanical toggle action type have been used for many years with cord sets and power supply cords for electric fans, portable lamps and various household appliances. Also, wall mounted mercury switches have gained wide acceptance in residential wiring for controlling the lighting circuits. This invention is believed to be the first that incorporates a mercury button switch in a feed-through cord switch to provide a smooth silent action.

The most serious disadvantage of most cord switches is that they incorporate a snap-acting toggle mechanism that requires a large force to operate the switch. When a. cord switch is assembled intermediate the ends of the cord, the switch must either be grasped in the palm of the 1 hand and operated by the thumb, or it must be held in .5 one hand and opera-ted by the other hand. In no case is it believed possible to operate standard cord switches by merely pressing directly on the switch handle. Hence,

- it "will be recognized that standard cord switches would not be practical for use in controlling table lamps where the switch is to rest on the top of the table and be operated by finger pressure exerted against the handle or switch actuator.

The principal object of this invention is to provide a feed-through cord switch with a silent, smooth acting switch mechanism that may be operated merely by direct y finger pressure exerted on the switch actuator.

A further object of this invention is'to provide a mercury feed-through cord switch with a lighted 't h actuator.

A further object of this invention is to provide a mercury feed-through cord switch with quick clamping means for connecting two cord ends to the switch contacts.

. A still further object of this invention is to provide a mercury cord switch with snubbing means on the bottom of the switch so that the two cords leading from the switch may extend from either end of the switch housing.

The switch of the present invention has a hollow housing comprising a flat base plate and a recessed cover member. A standard mercury button switch of the type shown in the Navias Patent No. 2,153,000, is rotatably, mounted in the cover between a pair of spring contacts. The top wall of the cover has an elongated opening in which is supported a switch actuator that is seated upon the mercury button. A. neon glow lamp and resistor assembly is carried within a hollow portion of the switch actuator, and the lamp leads are held in engagement with the opposite sides of the mercury button by pressure exerted by the switch actuator. The terminal ends of the switch contacts are sharpened into prongs for piercing the insulation of a parallel two conductor electric cord on which the cord switch is to be mounted. A bridging cont-act is also provided with insulation-piercing prongs so that the mercury button which is a single pole switch are combined therewith so. that the cords may be folded under the base plate and held firmly in place to enable the user to position the cords so that they both may extend from one end of the switch housing or from opposite ends.

My invention will be better understood from the following description taken in connection with the accompanying drawing and its scope will be pointed out in the appended claims.

Figure 1 is a side elevational view of a mercury through-cord switch embodying my invention.

Figure 2 is a cross-sectional elevational veiwpf the switchof Figure 1 takenthrough the'longitudinal center line thereof.

Figure} .is a cross-sectional elevational view taken through the transverse center line of the switch shown in Figure 2.

' Figure 4 is a bottom plan view of the switch of Fig ure 1.

Figure 5 is an exploded view of the cord switch of" Figure 1 showing the various elements of the switch, with the switch contacts shown twice, both disassembled and assembled in the recessed cover member.

Referring in detail to the drawing and in particular to Figure l, a preferred embodiment of my invention of a mercury through-cord switch is shown with a hollow housing 10' of insulating material comprising a generally flat base plate 11 and a recessed cover member 12. A

switch actuator 13 extends outwardly through anopening in the top wall of the cover 12 and is provided with two; finger-pressure areas 14 and 15 which are alternately engaged to change theposition of the switch.

Turning now to a consideration of the crosssectional viewof Figure Z, a fastening screw 16 is shown at each end of the housing 10. These screws extend upwardly from the bottomot the housing through suitable openings in the base plate 11 to engage in threaded holes in the cover'12.' A' standard mercury button switch 17,

as best seen in Figure 3, is assembled in the cover 12 in a center compartment defined by two parallelpartitions 18. 7 As will be well understood by those skilled in this art, the mercury button 17 has two metal cups 19 se'pa-' rated by a ceramic barrier (not shown), and a fused glass ring 20 joining the barrier and cups together. The ceramic barrier is provided with a hole so that separate pools of mercury retained in the metal cups 19 may flow together through the hole to complete an electric circuit that includes the metal cups as conducting elements. Accordingly, by oscillating the mercury button 17 about its central axis, the hole in the ceramic barrier will be made to dip into and out of the mercury pools, thereby closing and opening the circuit through the switch.

Each partition 18 supports a single switch contact 21 of thin sheet brass that is folded into an S-shape as best seen in Figures 3 and 5. The innermost end of each contact 21 has a semi-spherical bearing 22 that fits into. a mating surface in the side of the metal cup 19. The terminal end of each contact 21 is located on the outermost side of its supporting partition 18 and is sharpened into a prong 23 that is situated in a Wiring compartment 24f" A bridging contact 25, that is also fitted into the cover '12, is of generally 'U-shape with prong-like termi Patented Nov. 8, 1960.

nal ends 26 that are each arranged adjacentone of the prongs 23 of the switch contacts 21. The reason the switch contacts 21 and the bridging contact 25 have sharpened prongs 23 and 26, respectively, is to incorporate an insulation-piercing method of connecting the:

cord ends with the switch contacts. The-Benander et al. Patent No. 2,655,639, which is assigned 'to the same assignee as is the present invention, is one illustration of a table tap with insulation-piercing means having'a quick clamping action with the end of an electrical cord;

Now considering the exploded view of Figure 5, the

base plate 11 is shown with a pair of rectangular'openings 30 for cooperation with the wiring chambers 24 in the cover member 12. Each opening 30 has an opentop bearing 31 in its opposite side walls for receiving the trunnions 32 of a pivoted cam member or clamp 33. Each clamp 33 has a handle portion 34 and a pressure portion 35 that is adapted to exert a force on the electric cord to impale the cord on the prongs 23 and 26 of the switch contacts. The handle 34 is elongatedto' an extent that it will not pivot completely into the switch housing 10. This renders the clamps completely manageable from either an open or a closed position so that the average housewife may install the switch in the power supply cord of a table lamp without technical assistance.

The interior of the cover 12, as shown in Figure 5, has the two switch contacts 21 and the bridging con tact 25 positioned in place, while the mercury button 17 and the two cord ends are not present. Two cordreceiving openings 40 are formed in one end wall of' the cover. The base plate 11 is provided with a pair of guideways 41, each formed by a pair of parallel walls 42 that are arranged at the sides of each opening 40 and extend from the opening to the adjacent wiring chamber 24. An upwardly inclined surface 43 is provided in each guideway 41 and a parallel inclined surface 44 is present within the cover 12 so that the end of the cord must be thrust into the switch housing with an upward slant. Approximately midway between the opening 40 and the wiring chamber 24, the upwardly inclined surface 44 in the cover turns into a downwardly inclined surface 45 which forces the cord end to reverse I nermost tip of each downwardly inclnied surface 44 also' 1 serves as a strain relief shoulder for the cordand' assists in preventing the cord from being withdrawn from the switch housing when the clamps are closed over the cords.

Figure 5 also includes a neon glow lamp having a pair of leads 51. One lead is connected to an electrical resistor 52 so that the neon lamp and resistor are in series with each other and may be shunted across the metal cups 19 of the mercury button 17. Such a re sistor is a necessary adjunct to a neon lamp because a much greater voltage must be applied to the lamp to break down the initial resistance and light the lamp than the amount of voltage which is later continuously applied to maintain illumination. This high resistance effectively limits the amount of current that passes through the lamp, as only a very minute and almost immeasurable amount of current is required. The resistance also reduces the applied voltage used on the lamp by virtue of the resistance drop through the resistor after illumination has been effected.

Now turningto Figures 2 and 3 of the drawing, it will be seen that the switch actuator 13 is hollow, first to receive the top portion of the mercury button 17 and, secondly, to house the neon glow lamp and resistor as-v sembly 50 and 52. The switch actuator 13 has a pair of laterally projecting, curved flanges 55'which seat pr;

the metal cups 19 of the mercury button. On'such flange is provided with a downwardly extending tooth 56 for engagement in a depression 57 in the top of the underlying metal cup 19 so that the switch actuator 13 will be in driving engagement with the mercury button. Small pinholes (not shown) are formed on the underside of the flanges 55 for receiving the ends of the lead wires of the lamp and resistor assembly. Also, both flanges 55 are curved on their top surfaces for mating engagement with bearings 60 on the undersideof the top wall of the cover 10' adjacent the sides of an opening 62 through which the switch actuator 13 extends.

In order to insure good electrical contact between the metal cups 19 and the lead wires of the lamp assembly, a flat metal spring 65 is confined in the base plate 11 over a recess 66. Hence, as the fastening screws 16 are tightened in the cover member 12, the base plate 11 moves the spring 65 against the glass ring 20 of the mercury button 17, and the metal cups 19-press the curved flanges 55 of the switch actuator 13 into firm engagement with the side bearings 60 of the cover. This spring action also serves' to retard the rotation ofthe mercury button so that a positive manual force is neces sary to change the position of the switch. Small rubber pads 58 are fastened on the bottom of the switch actuprongs 23 and 26 of the switch contacts. It might happen 1 that the user of this switch would prefer one cord entering the switch housing at one end while the second cord would leave the switch housing at the other end. In this manner, the switch could be resting on a table top and one cord would be draped over the backof the table for connection with a wall-mounted convenience outlet. Another cord could be directed out of the other end of the switch so that it may enter the base of a table lamp. This' possibility has been designed into the switch, as will be 1 best understood by referring to Figures 3 and 4 of the drawings. The bottom surface of the base plate 11; as i seen in Figure 4, is anything but flat and simple. It ineludes two wireways 70 extending longitudinally along the sides of the base.

ends of each wireway 70 by asidewise projection 76 that extends from the portions 72 and 74. It should be understood that when the clamps 33 are closed, as shown 'in Figure 3, they are generally flush with the upper surfaces of the wireways 70. This is important because one or both of the electric cords that extend'outwardly-of'the switch housing from the openings 40 in the cover may" be bent sharply through 180 and-slipped through the Snubbing notch at each end of the -wireway 70 to be= and may readily be connected in the powersupply' cord of a table lamp by the average housewife. 'One of the primary features of this switch is that-it-is'a completely sealed unit and it is unnecessary to disassemble any part of the switch in order to connect it into the cofd of 'a lamp. All that is necessary isthat the cord'b'e cut in two leaving two cord ends. ,The two bare ends of the conductors of each cord endjwould then be separated slightly for about inch back from the end and then Each wireway is defined by an outer side flange 71 and raised central portions72, 73 and 74. Snubbing notches 75 are formed at the opposite the cord ends would be thrust into the openings 40 of the cover member 12 until they overlie the contact prongs 23 and 26. Then the clamps 33 would be closed over the cord ends, thereby forcing the prongs to pierce the insulation of the cords and make electrical connection with the conductors thereof. If it were desired to bring one cord out from each end of the switch housing, one such cord would be looped through the snubbing notches 75 of the wireway 70 and the switch would then be ready to place in operation.

Modifications of this invention will occur to those skilled in this art and it is to be understood, therefore, that this invention is not limited to the particular embodiments disclosed but that it is intended to cover all modifications within the true spirit and scope of this invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

l. A mercury feed-through cord switch comprising a hollow housing of insulating material, a pair of vertical partitions formed in the housing, an electrical contact member braced against the inner side of each partition, and a mercury button switch rotatably supported in said contacts, a switch actuator extending through the top wall of the housing and supported on the mercury button, the terminal end of each contact extending to the outer side of its respective partition and being in the form of a prong for piercing the insulation of an electrical conductor, and a bridging contact positioned in the housing with a prongshaped terminal at each end, each bridging contact prong being adjacent one of the other two contact prongs, whereby a wiring compartment is formed at the outer side of each partition and includes two parallel contact prongs facing toward the bottom wall of the housing, and a pivoted clamp extending through the bottom wall of the housing from each wiring compartment, a pair of cord-receiving openings in one end wall of the housing whereby two electrical cords may be inserted through the openings and into the wiring compartments to overlie the contact prongs and be impaled thereon by the closing of the clamps, and a spring member supported on the bottom wall of the housing and bearing against the underside of the mercury button to retard the turning movement of the button in its supporting contacts.

2. A mercury feed-through cord switch as recited in claim 1 wherein the switch actuator is hollow and contains a neon glow lamp and resistor assembly that has lead wires in engagement with the opposite ends of the mercury button, the said lead wires being held against the button by the switch actuator so that the upward pressure exerted by the spring in the bottom of the housing against the mercury button will maintain firm electrical contact between the lead wires and button.

3. A feed-through cord switch comprising a hollow housing of insulating material, a mercury button switch suspended between a pair of electrical contact members for rotation about an axis through the contacts, and a wiring compartment in the housing on each side of the mercury button, each compartment containing two contact prongs for piercing the insulation of a two conductor electric cord, one contact prong of each pair being the terminal end of the contact member that supports the mercury button, While the other contact prong of the pair is the terminal end of a bridging contact that has a contact prong in each wiring chamber so that the mercury button merely opens and closes one side of the line of the electric circuit, one end of the housing containing a pair of cord-receiving openings whereby two cord ends may be inserted into the housing and into the wiring compartments to overlie the contact prongs, and a pair of pivoted clamps extending through the bottom wall of the housing and movable into position against the cord ends to impale the cords onto the contact prongs, and a switch actuator seated on the top of the mercury button and extending through the top wall of the housing for rotating the mercury button into its circuit controlling positions, the switch actuator having arcuate flanges on its opposite sides bearing against complementary surfaces on the underside of the top wall of the housing, and spring means seated on the bottom wall of the housing and bearing against the mercury button to retard its movement so that a positive manual force must be applied to the switch actuator in order to change the setting of the switch.

4. A feed-through cord switch comprising a hollow housing of insulating material formed by a flat base plate and a recessed cover member, a mercury button switch suspended between a pair of electrical contact members in the cover for rotation about an axis through the contacts, and an opening in the top wall of the cover for receiving a switch actuator that engages with the mercury button, the switch actuator having arcuate side projections that bear against mating surfaces on the underside of the top wall of the cover, the bottom portion of the switch actuator having rubber-like pads that alternately engage the base plate when the actuator is oscillated between its two extreme positions to prevent the switch actuator from direct contact with the base, the terminal end of each contact being directed toward the base plate and sharpened into a prong for piercing the insulation of a cord brought in contact therewith, and a bridging contact having prong-shaped terminal ends, each end arranged adjacent one of the two before-mentioned contact prongs so that the mercury button acts as a single pole switch, one end wall of the cover having a pair of cord-receiving openings so that the end of a cord may be thrust into the cover to overlie each pair of prongs, and a pair of openings in the base plate with a pivoted clamp in each opening, each clamp being adjustable between an open and a closed position to force the cord ends into electrical engagement with the contact prongs, and spring means supported on the base plate and bearing against the mercury button to maintain firm engagement between the switch actuator and mercury button.

5. A feed-through cord switch as recited in claim 4 wherein the switch actuator is hollow and of translucent material, a neon lamp and resistor assembly located in the actuator and making electrical connection with the opposite sides of the mercury button, the lead wires of the lamp assembly being held into engagement with the rounded sides of the mercury button by means of the switch actuator.

6. A feed-through cord switch as recited in claim -1 wherein the bottom surface of the housing is provided with at least one wireway that extends longitudinally of the housing and is in line with one of said cord-receiving openings, the wireway being provided with snubbing means for confining a cord therein, so that a cord protruding from one end of the switch may be looped under the switch housing and held in the wireway for reversing the direction of the cord.

References Cited in the file of this patent UNITED STATES PATENTS 

